There have been many advancements in recent years in relation to extrusion-based additive construction, (hereinafter “EAC”), also commonly known as “fused deposition modeling” and “fused filament fabrication.” Regardless of which name is used, one unsolved challenge exists in relation to this technology; namely, a streamlined method for integrating a plurality of widely varying colors for EAC on an on-demand basis. Today, when using an extrusion-based additive construction printer for EAC, a thermoplastic filament is melted and subsequently extruded at specific points in a given horizontal (X, Y) plane.
This process is achieved when the filament used for construction travels through the print head of an EAC printer. Typically, this print head is comprised of two critical components: an “extruder” and a “hot end,” respectively. The extruder controls the rate at which the filament is fed into the hot end. The hot end reforms the filament by supplying heat sufficient to cause partial melting of the filament so that the semi-solid filament can be deposited at precise points on the horizontal (X, Y) plane through a nozzle, where each plane is constructed consecutively one at a time, and where each horizontal plane is stacked one on top of another in the vertical direction (Z). At the hot end, a controlled change of state of the material input occurs, where the filament is changed from a solid form to semi-solid form, allowing for its deposition. This process of planar construction is repeated at an integrally different vertical plane (Z), so that the previous plane serves as a support for the subsequent plane, until the desired object has been constructed.
Most EAC printers use thermoplastic construction material, such as a filament, which has been wound onto a spool. The manufacturers of these filaments are responsible for any color, or lack thereof, of the filament spool. Typically, this color is added to the filament by the use of mixing concentrated solid pigments called “masterbatches” with the other raw materials of the filament, resulting in a colored filament, which is then spooled.
In current methods of EAC 3D printing, the printed object bears the same color qualities as the filament feed used to create it. That is, in order to construct an object with a different color, the user must manually manipulate the extruder to accept a different, desired filament. This method carries with it three distinct disadvantages; it requires the user to stock filament spools of all the desired colors the user may wish to use in the EAC print; it limits the user to the colors of filaments that the manufacturers produce and supply; and this method requires the user to manually switch the machine's material feed for each change of color. As such, these methods of the prior art are limited by the availability of color filament choice which are offered by the manufacturers, which require the user's time and effort and technical skill while precluding the user's ability to print in different colors on-demand, remotely.
Some solutions in the prior art exist to overcome the aforementioned limitations of on-demand colorization in EAC. These solutions generally adhere to one of the following three guiding technical arrangements. The first involves a method which makes use of having a plurality of print heads, each having a filament with a unique color. The second solution involves making use of a single print head capable of accepting of a plurality of filaments, each filament having a unique color. Finally, the third guiding concept involves a method which makes use of having a single print head and a single filament where the filament is colored ‘upstream’ by the use of a series of color applicators, each applicator having a unique color, before reaching the print head.
In this first example, where colorized EAC is achieved through use of multiple printheads each with its own uniquely colored filament, the primary objective can be achieved. However, while this method solves many of the primary objectives such as colorization of a 3D model, the solution presents many other issues such as having to manually change the color of the filaments for each printhead when a new filament color is desired outside of what is already loaded into the head. Moreover, this method introduces new problems to EAC such as the back and forth motion in the horizontal direction of the printhead being required to be much slower due to the higher inertial forces involved in accurately positioning the multiple printheads, which are significantly heavier than the single-printhead variant. It should be noted that this multiple-printhead design can greatly increase the printing times, further reducing the efficiency of printing. This is due, in part, to the fact that only one printhead may be engaged at a time, and the active printhead must be brought into place before it may dispense the filament. In addition to the increased mass of having several print heads, there is now an issue of size; due to the fact that each printhead needs to be able to reach to every point in the horizontal plane of the object to be printed, the horizontal print area can reasonably be expected to be reduced, when compared to a printer having the same arrangement with only one printhead. This challenge can be overcome only by increasing the size of the EAC printer, however, this increased size introduces a multitude of problems, not the least of which is that the printer becomes too large to store in many places. This arrangement is both cumbersome to maintain and much too slow to be practical.
In general, the second method of having multiple filaments, each with a unique color, fed into one printhead overcomes many of the aforementioned problems. One example of this method is described in U.S. Pat. No. 8,827,685. In this method, colorization of EAC is achieved by individually controlling the rate at which each colored filament is pushed through the hot end. While at first blush this appears to be an elegant solution, the reality is that having several filaments feed into the hot end actually decreases the likelihood that each filament will each be properly heated so that it may be deposited on the build object. An imperfectly melted filament might not pass through the nozzle to become the build object, causing a jam. Further, the difficulty in heating can also affect whether each filament can mix proportionally and precisely after being heated to achieve the desired composite color before extrusion. Where there are several filaments which can be combined to give a desired color, imperfectly melted filaments can lead to a ‘swirly’ effect where each filament color is clearly identifiable as opposed to the desired composite color.
In the third method for the colorization of EAC, all of the aforementioned challenges can potentially be addressed. In this arrangement, a single virgin filament, upstream of the printhead, obtains new properties including color characteristics via a molecular coating specifically applied on the outer surface of the filament, as described in United States Patent Publication No. 2014/0134335. While this third option is the most attractive solution of the three approaches, in practice, this method is hampered by the fact that color is applied only to the surface of the filament. Spraying the surface of the filament with color leads to a reduction of the intensity of color of the extruded thermoplastic filament, and consequently the object being constructed. Additionally, this method also increases the probability that the colored surfaces of the filament will swirl around the uncolored (or lesser colored) innermost segments of the filament due to the nature of how the filament is heated and extruded; namely, specifically, this may happen due to the significant reduction in diameter of the filament between before extrusion, and after extrusion when the diameter is relatively smaller.
If only the surface area of the filament is colored, then the innermost segments of the filament will stay the original color of the filament. Perfect extruded color can only be achieved if the outside of the extruded thermoplastic is the outside of the filament input or if the filament before extrusion is a homogeneous color throughout its diameter. Because of the reduction in diameter of the filament after extrusion, the outside of the extruded plastic is not always the outside of the filament input, therefore allowing for some of the undyed interior color to show. This results in the overall effect of dulling the color of the constructed object or in the case of imperfect mixing before extrusion, having the overall effect of being ‘swirly’. The present invention and its embodiments meets and exceeds these objectives.
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Various systems and methodologies are known in the art. However, their structure and means of operation are substantially different from the present disclosure. The other inventions fail to solve all the problems taught by the present disclosure. The present invention and its embodiments take an approach for the colorization of EAC 3D printing, in a manner that provides for increased automation, reduced size, and higher productivity. At least one embodiment of this invention is presented in the drawings below and will be described in more detail herein.